Andrea Abi-Karam was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Andrea Abi-Karam was among 20 people arrested Saturday. San...

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Daniel Bash was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Daniel Bash was among 20 people arrested Saturday. San Francisco...

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Dante Cano was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Dante Cano was among 20 people arrested Saturday. San Francisco...

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Cicily Cooper was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Cicily Cooper was among 20 people arrested Saturday. San Francisco...

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Robert Donohoe was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Robert Donohoe was among 20 people arrested Saturday. San Francisco...

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Ariel Golan was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Ariel Golan was among 20 people arrested Saturday. San Francisco...

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Maria Lewis was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Maria Lewis was among 20 people arrested Saturday. San Francisco...

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Benjamin Mabie was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Benjamin Mabie was among 20 people arrested Saturday. San Francisco...

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Edward Medina was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Edward Medina was among 20 people arrested Saturday. San Francisco...

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Bryan Mitchell was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Bryan Mitchell was among 20 people arrested Saturday. San Francisco...

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Cammi Morgan was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Cammi Morgan was among 20 people arrested Saturday. San Francisco...

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Paul Murufas was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Paul Murufas was among 20 people arrested Saturday. San Francisco...

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Michael Pellagatti was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers. The district attorney's office dropped all charges against Pellagatti.

Photo: San Francisco Police Dept.

Michael Pellagatti was among 20 people arrested Saturday. San...

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Gabrille Silverman was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Gabrille Silverman was among 20 people arrested Saturday. San...

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Lauren Smith was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Lauren Smith was among 20 people arrested Saturday. San Francisco...

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Michael Thurman was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Michael Thurman was among 20 people arrested Saturday. San...

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Roth Upadhya was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Roth Upadhya was among 20 people arrested Saturday. San Francisco...

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Jami Williams was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Jami Williams was among 20 people arrested Saturday. San Francisco...

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May Young was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

May Young was among 20 people arrested Saturday. San Francisco...

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Laura Zelko was among 20 people arrested Saturday. San Francisco police officers arrested 11 men and nine women Saturday, Oct. 6, 2012 when the group marched through the city's Financial District in black clothing and tossed projectiles at police officers.

Photo: San Francisco Police Dept.

Laura Zelko was among 20 people arrested Saturday. San Francisco...

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Police photos of the weapons they say protesters threw at police officer on Saturday, October 6, 2012 in the city's Financial District.

Photo: San Francisco Police Department, Courtesy

Police photos of the weapons they say protesters threw at police...

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Police photos of the weapons they say protesters threw at police officer on Saturday, October 6, 2012 in the city's Financial District.

Photo: San Francisco Police Department, Courtesy

Police photos of the weapons they say protesters threw at police...

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Police photos of the weapons they say protesters threw at police officer on Saturday, October 6, 2012 in the city's Financial District.

Some of those arrested following a weekend vandalism spree in downtown San Francisco were probably involved in protests that caused damage in the Mission District last month, police said Monday.

San Francisco police arrested 11 men and nine women on Saturday when the group marched through the Financial District in black clothing and tossed projectiles at officers, said Officer Gordon Shyy, a police spokesman.

Police believe an anarchist group known as Black Bloc was involved, the same group police say was responsible for Mission District protests Sept. 20 and 21. Those protests occurred after officers shot and wounded a parolee who they say was armed. Protesters vandalized businesses and spray painted slogans on the Mission District police station. No arrests were made.

The same anarchist group was involved in Saturday's damage, Shyy said.

"It was the tactics of these individuals," Shyy said. "The masks, the hammers and some of the other weapons they had were consistent with the other protests we had encountered in the Mission."

Saturday's trouble began just before 3 p.m. when 100 marchers gathered at Justin Herman Plaza and headed up Market Street. A police officer was slightly injured when the demonstrators tossed flares, bags of paint and other objects. Several officers were bathed in paint.

Police officers circled the demonstrators around 3:30 p.m. at California and Battery streets, Shyy said. Other demonstrators were arrested when they fled to Pine and Sansome streets.

The 20 marchers were arrested on suspicion of conspiracy, rioting, refusing to obey a lawful order from a police officer, resisting arrest and assault on a police officer, Shyy said.

One of those arrested lives in San Francisco, Shyy said. The rest live in Oakland, Concord, Martinez, Newark, Mount Shasta (Siskiyou County), La Verne (Los Angeles County), Long Beach and San Diego.